In a house full of books we really don't need any more but when your local Post Office branch sells them at 25p for kids books, 50p for paperbacks and £1 for hardbacks* it's not hard to buy lots! It also doesn't help that it is a busy Post Office and having books to look at while you wait is a dangerous thing - for me anyway!
I'm currently one chapter off finishing one book (not really taken with it but I do want to see what happens next) and about 100 pages off finishing another so I *needed* to buy more :) Never mind the thousands sitting upstairs waiting to be read! And, with my pledge to only read books this year that I haven't read before, I needed to buy more just in case I ran out :D :D
*Those prices are why I now rarely buy books from anywhere else - can't go wrong when you can get 10 books for a fiver!